Axisymmetric numerical study of convective cloud electrification

An axisymmetric numerical model of convective electrification is presented. The model includes aerosols and small ions, and it takes into account the difference in mobilities between positive and negative small ions. The microphysics is represented by a bulk parameterization including cloud ice, cloud water, hail and rain. Although the results obtained with this model give the polarity structure most frequently observed in clouds, the characteristic times for charging appear to be longer than observed with electric fields too weak to produce lightning. The maximum electric field in a typical run reaches 8 kV/m in about 20 min. The charge conversion among particle categories arises as an important aspect previously overlooked in convective electrification. Based on these results it appears unlikely that the convective mechanism could be considered as the primary charging mechanism.